Key points:

Offensive seeks to break the government siege on rebel-held east Aleppo

Officials say at least a dozen people are killed, over 100 injured

Rebel groups detonated three large car bombs near pro-Government forces on the western edge of Aleppo, the Syrian Observatory for Human Rights and rebels said, as they tried to revitalise an offensive which has made little progress since taking most of Dahiyet al-Assad suburb on Friday.

They want to seize Government-held areas of Aleppo in order to link the city's east with rebel-held rural areas west of Aleppo.

The city has been divided for years between the Government-held western sector and rebel-held east, where the army launched a major Russian-backed offensive in September that medics say has killed hundreds.

United Nations aid has been unable to reach the besieged area since that time and the local medical infrastructure has been brought to its knees by a lack of supplies, a shortage of staff and air strikes on medical facilities.

Syrian state media said on Thursday 12 people were killed and around 200 injured by the rebel shelling on Government-held western Aleppo.

The Syrian Observatory for Human Rights said at least 15 civilians, including four children, had been killed in west Aleppo and around 120 injured.